**What**
- Add unit test that verifies the behavior of the logging middleware in
various reponse cases
Signed-off-by: Lucas Roesler <roesler.lucas@gmail.com>
* This experimental patch records metrics as invocations start
so that the metrics can be used to make better scale to zero
decisions in faas-idler.
Tested with Kubernetes on a single-node cluster, metrics
reported as expected. Existing metrics still report.
Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>